Golf ball

ABSTRACT

A golf ball includes a land part representing a symbol, and dimples defining the land part by outer edges thereof and disposed on a surface of the golf ball. The symbol represented by the land part may include numerals, letters, pictures, or logo. The dimples defining the land part by outer edges thereof can include at least two non-circular dimples. The dimples defining the land part by outer edges thereof can include a dimple having a wall surface having a linear shape extending substantially in a depth direction, the wall surfaces being adjacent to the land part representing the symbol.

BACKGROUND OF THE INVENTION

The present invention relates to a golf ball having a symbol.

Markings such as symbols, numerals, letters, and patterns are often applied on the surfaces of golf balls. Methods of applying such markings to the surface of a golf ball include methods of printing or transferring ink onto the surface of a golf ball and methods of engraving on the surface of the golf ball.

Because plural dimples are disposed at a high density on the surface of the golf ball, the former method has a problem of a tendency to yield poor printing. With the latter method, there is a problem of difficulty in engraving a marking such as a logo having a complex shape. Also, because the edges of the recessed parts are sharply pointed, there is the problem of an adverse affect on the aerodynamic characteristics of the golf ball.

U.S. Pat. No. 7,303,492 discloses a golf ball in which dimples are made into the shape of text letters or characters or other symbols. When a symbol is constituted by dimples, however, the symbol itself becomes very large, and in order to mark the surface of the golf ball with the desired symbol, there is the problem of an excessively large influence on the aerodynamic characteristics of the golf ball.

U.S. Pat. No. 7,273,426 and U.S. Pat. No. 7,618,332 disclose golf balls in which recesses having substantially uniform depth from the surface are formed in plural dimples and the land parts therebetween, wherein these recesses form patterns such as letters or graphic forms. The engraved marking to a depth that is substantially uniform can be formed simultaneously with the dimples when the cover layer of the golf ball is injection molded using a mold.

When the cover layer of a golf ball is molded, burrs often can occur at locations corresponding to the support pins and vent pins of the mold and to the seams. Because the presence of burrs greatly worsens the aerodynamic characteristics of the golf ball, it is necessary to remove them by grinding. When the golf ball is ground to remove burrs, there is the problem in that the depth of the engraved marking formed in the surface thereof is reduced, leading to the risk of destruction of the shape of the engraved marking.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a golf ball, which is based on a technological concept completely different from conventional dimples and engraved markings representing symbols, thereby providing a golf ball with a novel appearance.

A golf ball according to the present invention includes a land part representing a symbol, and dimples defining the land part by outer edges thereof and disposed on a surface of the golf ball. The symbol may include a numeral, a letter, a picture, or a logo. The symbol may represent a company, a trademark, a person, or a mascot character. The golf ball according to the present invention may include at least two of the land parts representing symbols. The dimples defining the land part by outer edges thereof preferably include at least two non-circular dimples.

The dimples defining the land part by outer edges thereof may include a dimple having a wall surface having a linear shape extending substantially in a depth direction, the wall surface being adjacent to the land part representing the symbol. The dimples defining the land part may include a dimple having a flat bottom surface. Preferably, a pole point of the golf ball may be arranged at a position within the land part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a golf ball according to an embodiment of the present invention.

FIG. 2( a) is a cross-sectional view showing an example of a dimple that defines a land part representing a symbol by its outer edge. FIG. 2( b) is a cross-sectional view showing another example of a dimple that defines a land part representing a symbol by its outer edge. FIG. 2( c) is a cross-sectional view of yet another example of a dimple that defines a land part representing a symbol by its outer edge.

FIG. 3 is a view illustrating a method of arranging dimples on the golf ball shown in FIG. 1.

FIG. 4 is a view showing a land part representing a symbol which is formed on the surface of a golf ball according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, plural dimples 10 are disposed on the surface of a golf ball 1. A golf ball surface between the plural dimples 10 is referred to herein with regard to the present invention as a land part 20. The land part 20 has a spherically curved surface that is a part of a surface of an imaginary sphere having its center at the center of the golf ball 1.

In general, the land part 20 that is surrounded by a plurality of circular dimples has an irregular and meaningless shape. In this embodiment, however, as shown in FIG. 1, a land part 22 has a shape representing the logo “Tour Stage,” which is a trademark of Bridgestone Sports Co., Ltd. The land part 22 representing the logo is defined by the outer edges of non-circular dimples 12.

A non-circular dimple, as the term is used in this specification, refers to a dimple having an outer edge, which is a boundary line 13 between a land part and a dimple, and which is not circular. The non-circular dimple, for example, includes a dimple having a bent part in the boundary line 13, and a dimple having the boundary line 13 formed by a curved part and a linear part.

As shown in FIG. 2( a), the cross-section of a non-circular dimple 12, in the same manner as a usual circular dimple, has a bottom surface 14 that is smoothly curved from the boundary line 13 with land parts 20, 22 toward the deepest position in the dimple center. As shown in FIG. 2( b), a wall surface 15 is preferably provided that is adjacent to the boundary line 13 a with the land part 22 representing a logo, and having a shape that is substantially a straight line in the depth direction. By providing such a wall surface 15, because the difference in height at the dimple surface at the boundary line 13 a between the dimple 12 and the land part 22 that represents the logo becomes prominent, the symbol such as a logo or the like represented by the land part 22 stands out visually.

In the case in which the wall surface 15 is provided, the part of the bottom surface 16 of the dimple from the position at which the dimple is deepest up until a part that is adjacent to the wall surface 15 may be made flat. Also, a smooth curve is maintained from the position at which the dimple is deepest up until the boundary line 13 b with the usual land part 20. It will be naturally understood that, as shown in FIG. 2( c), the wall surface 15 with a shape that is substantially a straight line in the depth direction may be provided adjacent to the boundary line 13 b with the usual land part 20, in which case the entire bottom surface 18 of the dimple is flat.

The depth of the non-circular dimple 12 at the deepest position is preferably, for example, at least approximately 0.05 mm, and more preferably at least approximately 0.10 mm. Also, the upper limit of the depth of the non-circular dimple 12 is preferably approximately 0.45 mm and more preferably approximately 0.35 mm.

The size of the non-circular dimple 12, that is, the maximum distance between two points on the outer edge 13 of the non-circular dimple 12, is preferably at least approximately 0.5 mm, and more preferably at least approximately 1 mm. Also, the upper limit of the size of the non-circular dimple 12 is preferably approximately 8 mm, and more preferably approximately 7 mm.

Because if the spacing between the outer edges of a plurality of non-circular dimples is too long, the land part 20 will become partially widened and could influence the aerodynamic characteristics of the golf ball, the spacing is preferably no greater than approximately 2.0 mm, and more preferably no greater than approximately 1.8 mm. Also, the lower limit of the spacing between the non-circular dimples 12, although not particularly limited, is preferably approximately 0.05 mm, and more preferably approximately 0.1 mm.

Although FIG. 1 shows the case in which the total number of dimples is 332 and there is one land part 22 representing a symbol, the present invention is not limited to this, and there may two or more land parts representing symbols. In the case in which a golf ball includes two or more land parts representing symbols, the symbols can either be the same or different. Preferably, the number of land parts representing symbols may be, but is not limited to, at most approximately six.

Preferably, the land part 22 representing a symbol may be arranged on the surface of the golf ball 1 such that a pole point 30 such as north or south pole of the golf ball falls within a region of the land part 22 representing a symbol, as shown in FIG. 3, but the present invention is not limited to this. A pole point of a golf ball usually is positioned at an end of a vent pin that is disposed along the axis of a die used to mold the golf ball (not shown). By using these arrangements, the burrs caused by the end of the vent pin can be easily removed by grinding. Dimples, including non-circular dimples, which form the land part 22 that represents a symbol by its outer edge, are arranged in one dimple pattern 32, with the other dimples being disposed in a plurality of dimple pattern units 34 in rotational symmetry about the pole point 30 as the center, so that even if the land part forms a symbol, it is possible to maintain a ratio of surface area occupied by dimples.

Although FIG. 3 shows the case of three-fold rotational symmetry with a rotational symmetry angle of 120°, the present invention is not limited to this, and may have, for example, four-fold, five-fold, or six-fold rotational symmetry. In the case of a golf ball mold that splits apart top and bottom, if the vent pin is positioned at a pole point 30, the parting seam between the top and the bottom parts of the mold is positioned at the equator 36 of the golf ball 1. As an alternative to the embodiment shown in FIG. 3, the land part representing a symbol may be disposed on the surface of the golf ball so that the parting line passes through the region of the land part that represents the symbol.

The total number of dimples, including non-circular dimples, formed on the surface of the golf ball, is preferably at least approximately 150, more preferably at least approximately 200, even more preferably at least 250, and still more preferably at least approximately 300. Also, the upper limit on the total number of dimples is preferably approximately 500, more preferably approximately 400, and even more preferably approximately 360.

The proportion of surface area occupied by the dimples, including non-circular dimples, is preferably at least approximately 70%, and more preferably at least approximately 80%. Also, although there is no particular restriction, from the standpoint of providing a land part 22 to represent a symbol, the upper limit of the proportion of the surface area occupied by the dimples is preferably approximately 90%.

Although FIG. 1 shows the case in which one land part 22 that represents one symbol is formed by the outer edges of the eight non-circular dimples 12 a through 12 h, the present invention is not limited to this, and it is possible to form one land part that represents one symbol by the outer edges of at least two non-circular dimples, without greatly influencing the aerodynamic characteristics of the golf ball. More preferably, at least three non-circular dimples are used. The upper limit on the number of non-circular dimples that form a land part that represents one symbol is preferably approximately 15, and more preferably approximately 12, although the present invention is not limited to this.

Although FIG. 1 shows the case in which the land part 22 represents a logo as a symbol, the present invention is not limited to this, and the symbol represented by the land part may include a numeral, a letter, or a picture and the like, as well as a logo. By using one or more symbols such numerals, letters, pictures and logos, it is possible to represent a company, a product, a trademark, a person or a mascot character. These may be related to golf or to balls, or may not be directly related to golf or to balls.

For example, as shown in FIG. 4, it is possible to form six land parts 40 that represent the six letters N, E, W, I, N, and G. The six land parts spell NEWING, a trademark of Bridgestone Sports Co., LTD. The land part that represents the letter “N” is formed by the outer edges of the four non-circular dimples 42 a through 42 d. The land part that represents the letter “W” is formed by the outer edges of the seven non-circular dimples 42 d through 42 j. The land part that represents the letter “l” is formed by the outer edges of the two non-circular dimples 42 i and 42 j.

Although FIGS. 1 and 4 show the cases in which the land parts 22, 40 that represent symbols are all formed by the non-circular dimples 12, 42, the present invention is not limited to this, and whether a dimple has a circular or non-circular shape when viewed from above is determined by the shape of the symbol, which may also, of course, be formed by the outer edges of circular dimples.

In the same manner as in the case of the usual circular dimples, the non-circular dimples that form land parts representing symbols by their outer edges can be formed in the process step of forming the cover layer of the golf ball. Specifically, the cover layer is formed by injection molding of the cover layer material into a die. The die for the cover layer (not shown) has a cavity wall surface for the purpose of forming the surface of the land part and concave parts protruding from the cavity wall surface for the purpose of forming dimples.

The die may be fabricated by using 3-dimensional CAD or CAM and by using a method in which an overall surface shape is directly and three-dimensionally formed in a reversing master die, or a method in which a cavity part of the die is directly and three-dimensionally machined.

Materials for the cover layer may be, but are not limited to, an ionomer resin, a polyurethane-based thermoplastic elastomer, or thermoplastic polyurethane. The golf ball may be of one-piece structure or of a multiple-piece structure having two or more pieces.

While a golf ball according to the present invention has been described in connection with preferred embodiments, it is not intended to limit the scope of the invention to the particular form set forth, and on the contrary, it is intended to cover such alternatives and modifications as may be included within the spirit and scope of the invention as defined by the appended claims. 

1. A golf ball comprising: a land part representing a symbol; and dimples defining the land part by outer edges thereof and disposed on a surface of the golf ball.
 2. The golf ball according to claim 1, wherein the dimples defining the land part by the outer edges thereof comprise at least two non-circular dimples.
 3. The golf ball according to claim 1, wherein the dimples defining the land part by the outer edges thereof comprise at least three non-circular dimples.
 4. The golf ball according to claim 1, wherein the dimples defining the land part by the outer edges thereof comprise a dimple having a wall surface having a linear shape extending substantially in a depth direction, the wall surface being adjacent to the land part representing the symbol.
 5. The golf ball according to claim 1, wherein the dimples defining the land part comprises a dimple having a flat bottom surface.
 6. The golf ball according to claim 1, wherein a pole point of the golf ball is arranged at a position within the land part.
 7. The golf ball according to claim 1, wherein the symbol comprises a numeral.
 8. The golf ball according to claim 1, wherein the symbol comprises a letter.
 9. The golf ball according to claim 1, wherein the symbol comprises a picture.
 10. The golf ball according to claim 1, wherein the symbol comprises a logo.
 11. The golf ball according to claim 1, wherein the symbol represents a company.
 12. The golf ball according to claim 1, wherein the symbol represents a product.
 13. The golf ball according to claim 1, wherein the symbol represents a mascot character.
 14. The golf ball according to claim 1, comprising at least two of the land parts representing symbols. 